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Liquid rubber vs silicone

Updated: 23 October 2026

You searched liquid rubber vs silicone because a listing said silicone, a cartridge in the shed said silicone, and a kit for moulds said silicone rubber as well. Those are three products. A cold roof film keeps water off a sound deck. A bead or a gap coating closes a joint. A 1:1 mould silicone copies a master in resin, wax, plaster or soap. None of them does the other two jobs. A mould kit will not stop a shed leak, and a roof coating will not cast a clean resin part. The [liquid rubber comparison](/hub/fillers-adhesives-and-sprays/liquid-rubber) ranks a mixed set. This page only separates the silicone fork. A qualifying purchase through our links can earn us a commission at no extra cost to you.

You searched liquid rubber vs silicone because a listing said silicone, a cartridge in the shed said silicone, and a kit for moulds said silicone rubber as well. Those are three products.

Our top picks

Gorilla Gorilla Waterproof Coat & Seal, black, 473 ml

Best overall

Gorilla Gorilla Waterproof Coat & Seal, black, 473 ml
9.0/10about £19.30
View offer
STARTSO WORLD STARTSO WORLD platinum mould silicone, 20A

Rank 2

STARTSO WORLD STARTSO WORLD platinum mould silicone, 20A
9.0/10about £24.29
View offer
WYCOON WYCOON translucent mould silicone, 1.1 kg

Rank 3

WYCOON WYCOON translucent mould silicone, 1.1 kg
8.4/10about £22.94
View offer
On this page
  1. 1.Three products the search treats as one
  2. 2.Leak or joint, not a mould
  3. 3.Mould rubber, and why it stays tacky
  4. 4.Food contact is a document, not an adjective

Three products the search treats as one

A trade silicone roof coating is a film some contractors use where water lingers. Do not read that ponding claim onto STARTSO, WYCOON or Gorilla. In this set, a Skyguard-type sheet is a cold film at about 1 litre per square metre. Gorilla is a brush-on gap coating to 6 mm, not a garage roof and not a mould. Shore A, on STARTSO’s 20A, is a stiffer mould. Shore 00, on BBDINO, is skin-soft. Nakutita is a squishy-toy kit. A dry shed and a mould are different buys.

Leak or joint, not a mould

A measured joint is Gorilla’s liquid, not a mould pour. The UK page allows gaps up to 6 mm, at 10–48 °C, with a full cure of 24–48 hours, and bars large areas, flashing, and engine zones. The 946 ml listing adds pipes under pressure and a firebox. Tape covers about 6–99 mm. The 473 ml tin is one joint. The 946 ml tin is several local patches. Both share 4.5 from 2,378 reviews, including clear-coat comments, so buy the black title. A silicone cartridge is a gunned bead, often not paintable, and it is not a row here. Use a cartridge for a bead, the liquid inside 6 mm, tape above that, and a roof coating for square metres of sound deck.
Gorilla Gorilla Waterproof Coat & Seal, black, 473 ml

Testsieger

Gorilla Gorilla Waterproof Coat & Seal, black, 473 ml
9.0/10about £19.30
View offer

Mould rubber, and why it stays tacky

STARTSO’s 20A platinum is about 38 oz at about £24.29, mixed 1:1, 4.5 from 741 reviews, with a seller window of about 4–6 hours at 23 °C. The URL is B0CWV2TLYM and the specification block prints B0CWV152N4. WYCOON is about £22.94, seller Shore 15A, and the notes warn against curing under 18 °C. BBDINO at about £38.97 is Shore 00-30, and a thin mould slumped. Platinum often stays tacky against sulphur clay, latex and tin-cure silicone. Smooth-On says Mold Star will not cure against sulphur even if you seal it, and it specifies vinyl gloves. Test a patch. Roof rates are on how to apply liquid rubber.

Food contact is a document, not an adjective

A mould that set overnight is not cleared for food. Assimilated Regulation 1935/2004 is the UK duty. Food grade, or an FDA line, is not that declaration. STARTSO’s seller says food grade for sweets and chocolate. Do not cast a fatty mix unless the declaration is with the tin. A 6 mm gap is Gorilla or tape. A master is STARTSO or WYCOON only near 23 °C, and not against sulphur, latex or tin-cure silicone.

Common questions

Is liquid rubber the same as silicone sealant?
No. In this set, liquid rubber is either a roof film or Gorilla’s brush-on gap coating to 6 mm. A silicone sealant is a cartridge bead, often not paintable, and it is not a row here. A 1:1 mould silicone is a third product. A trade article about silicone roof coating is not talking about STARTSO or a cartridge.
Can a 1:1 mould silicone stop a shed leak?
No. STARTSO and WYCOON are pourable mould rubbers for resin, wax, plaster, candle or soap. They are not rated as a roof coating, and platinum can stay tacky against the wrong master. A shed leak wants a roof film at about 1 litre per square metre, or Gorilla if the fault is a gap up to 6 mm.
When is a cartridge right, and when is Gorilla’s liquid?
Use a silicone cartridge when you need a gunned bead in a joint. Use Gorilla’s liquid when you can brush a gap up to 6 mm, at 10–48 °C, and wait 24–48 hours. Use patch tape once the gap is over 6 mm, up to about 99 mm on Gorilla’s membrane guide. Neither one coats a 5 m² roof.
What is Shore 00 versus Shore A here?
Shore A, such as STARTSO’s 20A or the seller’s 15A on WYCOON, is a stiffer mould that can hold shape. Shore 00-30, on BBDINO at about £38.97, is skin-soft. Reviews say a thin 00-30 mould slumps and the surface stays tacky. Buy 00-30 for a flesh prop. Do not treat BBDINO as platinum.
Why did the mould stay sticky against the clay?
Platinum is easily inhibited by sulphur clay, latex and tin-cure silicone. Smooth-On states that Mold Star will not cure against sulphur even if you seal it, and latex gloves can inhibit the surface. A tacky face with a cured back is that failure. Test a patch and switch to vinyl gloves. A sealer is not a guarantee.
Does platinum or FDA mean the mould is cleared for UK food?
No. Food contact in the UK is assimilated Regulation 1935/2004. An FDA line, or food grade on the title, is not that declaration. None of these listings includes one. A buyer who washed a mould and waited longer was being careful. That story is not a certificate for chocolate or a fatty food.

Related pages

Liquid rubber buying guide

Liquid rubber for a roof and gutter

Best liquid rubber

Liquid rubber

How to apply liquid rubber: prep, temperature and cure

Sources

Public UK sources used for this comparison. amazon.co.uk prices, stars and review counts were taken from the listings on 19 October 2026.

  1. Skyguard liquid rubber data sheet (retrieved 19 October 2026)
  2. Skyguard 5 litre liquid rubber (retrieved 19 October 2026)
  3. Gorilla Waterproofing Liquid Black (UK) (retrieved 19 October 2026)
  4. Bostik Waterstop flexible waterproof coating (retrieved 19 October 2026)
  5. HSE paint and coatings FAQ (retrieved 19 October 2026)
  6. HSE latex allergy (retrieved 19 October 2026)
  7. Bauder on BS 6229:2025 (retrieved 19 October 2026)
  8. Assimilated Regulation 1935/2004 (retrieved 19 October 2026)
  9. Plasti Dip liquid electrical tape (retrieved 19 October 2026)